Industrial Hygiene in Construction

This post will be an attempt to describe the hazard of the heavy metal, hexavalent chromium.  The subject is confusing. It’s a technical subject, and I will try to make it simple to understand.  If you have questions you can contact Julia Roberts,  from the movie Erin Brockovich.  (This was the one of the contaminants in the water in that movie/documentary)

Chromium is a metal found as chromium-3 (it’s valence) – and…if you remember from chemistry, the valence is the number of positive charged ions.  The point: when chromium is heated, it “becomes” chromium-6, or hexavalent chromium.  Hexavalent chromium will eventually go back to chromium-3. I believe the half-life is about 17 days (it takes 17 days for half of the material to convert back from cr6 to cr3).  Here’s the confusing part:  Chromium-6 isn’t harmful, but it is VERY able to be absorbed by your body (skin & membranes).  Chromium-3 is harmful, but isn’t able to be absorbed by your skin.

So, here’s what happens:

1. you have a material (or a product, ie. stainless steel, or look at your MSDS) with chromium-3 in it.
2. you heat it up
3. it turns into chromium-6 (hexavalent chromium)
4. it absorbs into your body (breathe, drink, touch)
5. it goes back to chromium-3
6. you develop symptoms/disease

Symptoms might include:   irritation or damage to nose/throat/lung, chrome ulcers (gross, huh?), lung cancer (if breathed), eye damage, allergic response (including dermatitis).

In construction we typically see exposures in these activities:

• Welding
• Stainless steel metal-work
• Painting- (as a pigment) or an anti-corrosion agent
• Hardfacing – applying weld-beads to the sides of loader buckets (see picture)

The risk of high exposure varies due to many factors including, type of work, ventilation, amount of chromium in the product, etc.

The CDC has some good information here.

Controls:  As usual, it depends. However, as a general rule you should try and eliminate the hazard (use non-chrome materials, or add ventilation). If it is still of concern, use administrative controls (limit the time, make sure employees are following protocols). And, finally, personal protective equipment to control exposures. Proper respirators (with HEPA cartridges) and don’t forget skin protection (gloves, tyvek, etc.).

Some workers were performing MIG (gas metal arc) welding and subarc welding. This is a daily task and their employer requested that we measure the air – as a general assessment tool. In other words, employee’s weren’t concerned, and no one was complaining, but they wanted to explore further into this aspect of their employee’s health and wellness.

We performed air monitoring and analyzed as a welding fume profile which is a number of commonly found welding metals including:

• Antimony
• Beryllium
• Cadmium
• Chromium
• Cobalt
• Copper
• Iron Oxide
• Lead
• Manganese
• Molybdenum
• Nickle
• Vanadium
• Zinc Oxide

Along with the welding fumes, we ran a sample for hexavalent chromium using OSHA Method ID215.

Nowhere in the MSDS (material safety data sheet) did it list “chromium” in the material make-up. However, knowing that it could be a trace metal it might be an issue. MIG welding (in general) isn’t typically of high concern for this hazard. And, as it turns out, the results were found to be below their respective limits.

Employees were not welding the entire day.  At least half of the time was spent fitting, moving, tacking, remeasuring, and gathering materials. Noise was a big issue as well. Most of the day it was quiet, but when the steel would drop, or an “adjustment” to the metal was needed…it was usually followed by a hammer-bang.  Honestly, without the ear plugs, it scared me.